Sequential loading system having auxiliary switches

ABSTRACT

A sequential loading control system including a plurality of main switches controlling current flow to respective loads. Respective time delay drive means are provided for controlling the respective main switches and respective auxiliary switches are mechanically coupled with the main switches to form respective units and are closed when the main switches are closed. Circuit means connects the main switches to the respective loads and the auxiliary switches of each unit with the time delay drive of the succeeding unit whereby energization of the system results in the respective time delay drive means being sequentially energized to effect closure of the respective main switches and also the auxiliary switches to energize the time delay means of the succeeding unit to thereby sequentially bring the loads into the circuit.

Uited States McIntosh atent 11 1 SEQUENTIAL LOADING SYSTEM HAVINGAUXILIARY SWITCHES [75] Inventor: Harold A. McIntosh, South Pasadena,Calif.

[73] Assignee: Robertshaw Controls Company,

Richmond, Va.

[22] Filed: Jan. 31, 1972 [21] App]. No.: 222,107

[ Nov.6,1973

Primary Examiner-Herman J. Hohauser Att0rneyVern Schooley et al.

[ 57] ABSTRACT A sequential loading control system including a plurality of main switches controlling current flow to respective loads.Respective time delay drive means are provided for controlling therespective main switches and respective auxiliary switches aremechanically coupled with the main switches to form respective units andare closed when the main switches are closed. Circuit means connects themain switches to the respective loads and the auxiliary switches of eachunit with the time delay drive of the succeeding unit wherebyenergization of the system results in the respective time delay drivemeans being sequentially energized to effect clo- [56] R fer n Cit dsure of the respective main switches and also the auxil- UNITED STATESPATENTS iary switches to energize the time delay means of the 3 634 80]H1972 G M 337/340 succeeding unit to thereby sequentially bring theloads 0U 2,958,755 11/1960 Miller 219/486 x the Gram" 2 Claims, 7Drawing Figures 53 a E v J /Z/ 1V7 63 r as A33 f'L SEQUENTIAL LOADINGSYSTEM HAVING AUXILIARY SWITCHES BACKGROUND OF THE INVENTION spectiveloads. A device of this type incorporating thermostatic blades connectedin series with the respective loads is shown in US. Pat. No. 3,588,471.This device suffers the shortcoming that each load is connected inseries with the time delay resistor of the succeeding unit therebyrequiring relatively carful design control for the particularthermostatic blade and heating resistors for various different sourcevoltages and required time delays.

SUMMARY OF THE INVENTION The present invention is characterized by asequential loading control system including a plurality of main switchesconnected in series with respective loads and being driven by electricaltime delay means. Respective auxiliary switches are mechanically coupledto each of the main switches and are closed thereby as such mainswitches are closed to energize the time delay means of the succeedingunit to, after a selected time delay, effect closure of the main switchof such succeeding unit.

The objects and advantages of the present invention will become apparentfrom a consideration of the following detailed description when taken inconjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a time delayrelay device incorporated in a control system embodying the presentinvention;

FIG. 2 is a bottom view of the time delay device shown in FIG. 1;

FIG. 3 is a longitudinal sectional view, in enlarged scale, taken alongthe line 3-3 of FIG. 2;

FIG. 4 is a longitudinal sectional view taken along the line 4-4. ofFIG. 3;

FIG. 5 is a longitudinal sectional view, taken along line 4-4 of FIG. 3;

FIGS. 5 and 6 are transverse sectional views taken along the line 5-5 ofFIG. 4; and

FIG. 7 is a schematic diagram of a sequential loading control systemembodying the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 7, thesequential loading control system of present invention includes,generally, a plurality of thermostatic main control switches 21, 23, 25and 26 for controlling a current to respective resistance heater loads27, 29, 31 and 32. The respective main control switches 21, 23 and 25are mechanically coupled with respective auxiliary switches 35, 37 and39 to form respective units. Respective resistance heat motors 41, 43,45 and 46 are disposed in heat exchange relationship with the respectivethermostatic switches 21, 23, 25 and 26 whereby, upon energization ofthe resistance heat motor 41 of the first unit, the first thermostaticswitch 21 will be closed to energize the resistance heater load 27 andclose the associated auxiliary switch 35 to energize the resistance heatmotor 43 of the second unit to commence heating of the secondthermostatic main switch 23. After a selected time delay, such secondthermostatic switch 23 will close to energize the second resistanceheater load 29 and close the auxiliary switch 37 thereby energizing thetime delay heat motor 45 of the third thermostatic switch 25 to energizethe third resistance heater load 31. Consequently, the loads 27, 29 and31 are brought sequentially into circuit to thereby avoid simultaneousenergization of all loads and consequent overloading of the powersource.

In the particular embodiment shown the sequential loading control systemof present invention is utilized for controlling operation of a forcedair furnace in response to temperatures sensed by a thermostat 49. Thefirst unit heat motor 41 is connected across the secondary coil of asource transformer 51 and in series with the thermostat 49 by means ofleads 53, 55 and 57. The primary coil of such transformer 51 isconnected across a pair of source terminals 58 and 59 by means of leads60 and 62.

The furnace (not shown) incorporates the four resistance heater loads27, 29, 31 and 32 and a blower 69 is provided for blowing air thereover.Current to such blower 69 is controlled by a thermostatic blower switch71 that is disposed in the plenum chamber of such furnace and arrangeddownstream of such resistance heater loads.

The first time delay switch 21 is connected across the source terminals58 and 59 and in series with the resistance heating load 27 by means ofleads 73, 75, 77, 79 and 81. The thermostatic blade of the time delayswitch 21 is connected with one terminal of the fan switch 71 by meansof a lead 87, the thermostatic blade 89 of such fan switch beingconnected with the negative terminal of the fan 69 by means of a lead 91and the positive terminal of such fan being connected with one of thesource terminals 59 by means of a lead 95.

The second heater load 29 is connected between the source terminals 58and 59 and in series with the second unit thermostatic switch 23 bymeans of leads 73, 101, 105, 107 and 81. The stationary contact of thesecond thermostatic switch 23 is connected with the normally opencontact 111 of the fan control switch 71 by means of a lead 113.

The resistance heater load 31 of the third unit is connected across apair of source terminals 117 and 119 and in series with the thirdthermostatic switch 25 by means of leads 121, 123, 125, 127 and 129.

The fourth resistance heater load 32 is connected across theterminals.117 and 119 and in series with the fourth thermostatic switch26 by means of leads 121, 131, 133 and 129.

The second resistance delay motor 43 is connected across the secondarycoil of the transformer 51 and in series with the first auxiliary switch35 by means of leads 55, 135, 137, 139 and 53.

The third resistance delay drive motor 45 is also connected across thesecondary coil of the transformer 51 and in series with the secondauxiliary switch 37 by means of leads 55, 135, 139, 141, 139 and 53.

The fourth resistance delay motor 57 is also connected across thesecondary coil of the transformer 51 and in series with the thirdauxiliary switch 39 by means of leads 55, 135, 139, 153, 155, 157, 147,and 53.

Connected in series with the respective resistance loads 27, 29, 31 and61 are protective devices in the form of respective fusible links 158and limit switches 160.

The respective time delay switches 21, 23 and 25 and auxiliary switches35, 37 and 39 are mounted in respective relay housings 161 (FIG. 2).Referring to FIGS. 2 and 3, the relay housing 161 has a stationarycontact 167 mounted thereon and a movable contact 159 disposed inengagable alignment therewith. The movable contact 169 is carried fromthe free end of a cantileverly mounted tri-snap blade 171. The tri-snapblade 171 is of a character that after the free end thereof has moveddownwardly a predetermined distance, it will flex and snap rapidlydownwardly to close the movable contact 169 on the stationary contact167. The stationary contact 167 is connected with a plug prong 175 andthe movable contact 169 is electrically connected with a plug prong 177.Respective set screws 179 and 181 are provided for adjusting the actionof the tri-snap blade 171.

Referring to FIG. 3, movement to the right of the free end of thetri-snap blade 171 is normally resisted by an electrically insulatingcoupling bar 185 which is formed in its left extremity with a throughslot 187 having the free end of a compensating thermostatic blade 191projecting therethrough. The opposite extremity of the compensatingblade 191 is urged upwardly against an adjustment screw 193 by means ofan electrically conductive thermostatic blade 195. The thermostaticcompensating blade 191 and thermostatic drive blade 195 are arranged inopposed relationship such that heating of the blade 195 causes the freeend thereof to move to the right as viewed in FIG. 3 while the free endof the compensating blade 191 moves an equal distance to the left forequivalent heating to thereby compensate for ambient heating of suchblade.

As best seen in FIG. 2, the first heat motor 41 is in the form ofaresistance heating coil wound on the thermostatic blade 195, such coilhaving a lead 200 connecting it with a plug prong.

Still referring to FIG. 3, mounted interiorly at the upper end of thehousing 161 is the auxiliary switch 35. Referring to FIGS. 5 and 6, theauxiliary switch 35 is in the form of a pivotable rivet 201 having aresilient electrically conductive arm 203 projecting therefrom.

stationary contacts and such rivet 201 then riveted over to be securedagainst further rotation.

Disposed exteriorly of the housing 153 are a pair of tabs 217 and 219which are mounted from the respective electrically conductive rivets 209and 201 and are bent outwardly to form plug prongs as shown in FIG. 3.

In operation the source terminals 58 and 59, 117 and 119 are connectedto a power source to energize the system. When the thermostat 49 sensesa selected load temperature, it will close a pair of internal contactsto energize the first time delay resistor 41 to commence heating of thefirst thermostatic switch 21. Referring to FIG. 2, heating of theresistance windings 41 heats the thermostatic blade 191 and flexes thefree end thereof to the right as viewed in FIG. 3 thereby enabling thefree end of the tri-snap blade 171 to move to the right and also movingthe auxiliary drive rivet 211 upwardly as viewed in FIG. 5. When thefree end of the tri-snap blade 171 has moved sufficiently far to theright to initiate snapping thereof the movable contact 169 will besnapped downwardly into engagement with the stationary contact 167.Immediately prior to engagement of the movable and stationary contacts169 and 167, the free end of the movable auxiliary switch arms 203 (FIG.5) engages the stationary arm 207 to thereby close the auxiliary switch35. Closure of the switch 37 takes the bias of the auxiliary switch armoff the drive rivet 211 thereby preventing the bias of such arm addingto any tendency of the movable contact 169 to bounce off the stationarycontact 167 upon engagement of such contacts to thereby avoid theconsequent arcing as the contact 167 and 169 close.

Closure of the thermostatic switch 21 completes a circuit through theleads 73, 75, 77, 79 and 81 to energize the heating resistor load 27 andinitiate furnace heating. Also, closure of such thermostatic switch 21completes a circuit through the leads 73, 75, 87, 91 and 95 to energizethe blower 69 to commence blowing air over the resistance heater load 27to commence forced air heating of the environment as well as to avoidoverheating of such heating loads 27.

The forced air from the blower 69 passing over the heater load 27 willbe heated to heat the fan switch 71 i to flex the thermostatic blade 89upwardly to the bro- Disposed in alignment with the free end of the arm203 is an electrically conductive stationary arm 207 which is carriedfrom a second pivotable rivet 209. A drive peg 211 is mounted centrallyon the coupling bar 185 and is formed with a head 213 having theintermediate portion of the resilient movable arm 203 engagedtherebehind. Consequently, when the switch 35 is assembled, the mountingrivet 209 for the stationary arm 207 may be rotated to orient thestationary arm 207 at the desired angularity for closure of the switch35 at a specified time with respect to closure of the thermostaticswitch 21 and the rivet 209 then riveted over to secure such stationaryarm 207 against further pivoting. Likewise, the rivet 201 mounting themovable arm 203 may be rotated or orient the movable arm 203 at thedesired angularity for providing the desired switch closing time andcontact pressure between the movable ken line position to engage thecontact 111 connected with the source terminal by means of the leads 73and 113. Thus, the fan 69 will remain energized until all the heatingloads 27, 29, 31 and 61 are de-energized and the thermostatic switch 71allowed to cool.

Closure of the first auxiliary switch 35 commences current flow throughthe heat motor 43 of the second delay switch 23 and, after apredetermined time, the thermostatic blade 191 thereof will be heatedsufficiently to flex and close the second time delay switch 23 toenergize the second heater resistance load 29.

Referring to FIG. 1, closure of the second auxiliary switch 37 (FIG. 7)commences current flow therethrough and through the heat motor 41 of thethird time delay switch 25 to initiate heating of the thermostatic blade191 and consequent flexure to close the third auxiliary switch 39 andmain switch 25 to energize the fourth heat motor 46 and third resistanceheater load 31.

After a fourth time delay, the resistance motor 46 will heat the fourthtime delay switch 26 sufficiently to effect closure thereof andconsequent energization of the fourth resistance load 32.

The resistance heater loads 27, 29, 21 and 32 will then remain energizeduntil the environment is warmed sufficiently to warm the thermostat 49above the target temperature to open the internal contacts to deenergizethe first resistance delay motor 41 to enable the first time delayswitch 21 to cool and open thereby opening the first auxiliary switch 35and de-energizing the first resistance load 27. Opening of the firstauxiliary switch 25 will enable the second time delay motor 43 to coolto cause the second time delay switch 23 to open thereby opening thesecond auxiliary switch 37 and also de-energizing the second resistanceload 29. Opening of the second auxiliary switch 37 will enable the thirdtime delay resistance motor 45 to cool thereby enabling the third timedelay switch 25 to open thereby opening the third auxiliary switch 39and also deenergizing the third resistance load 31.

Opening of the third auxiliary switch 39 will enable the fourth timedelay resistance 46 to cool thereby causing the fourth time delay switch26 to open to deenergize the fourth resistance load 32.

The fan motor 69 will remain energized until all the resistance loads27, 29, 31 and 32 have cooled thereby enabling the fan switch 71 to coolto flex the free end of the thermostatic blade 89 downwardly to therebyopen the circuit to the fan 69 to discontinue operation thereof.

From the foregoing, it will be apparent that the sequential loadingcontrol system of present invention provides a convenient means forsequentially bringing a plurality ofloads into circuit to thereby avoidsimultaneously loading the circuit with all such loads and reducing therisk of overloading the electrical source.

Various modifications and changes may be made with regard to theforegoing detailed description without departing from the spirit of theinvention.

What is claimed is:

l. Sequential loading control system comprising:

a plurality of loads;

a plurality of relay housings;

respective main switches mounted in the respective housings andincluding respective first and second contacts, thermostatic blade meansmounted on one end to said respective housings and carrying saidrespective second contacts on the free ends thereof for travel through apath into engagement with said respective first contacts upon flexure ofsaid respective blade means;

respective auxiliary switches mounted in the respective housings andincluding respective stationary contacts and elongated resilient andelectrically conductive arms mounted on one end from the respectivehousings and having the free ends thereof formed to define respectivehousings and having the free ends thereof formed to define respectivemovable contacts disposed for engagement with the respective stationarycontacts upon flexure of said respective arms, said arms beingmechanically coupled with the respective thermostatic blades to formrespective units;

respective time delay drive means including heat motors disposedadjacent each thermostatic blade;

actuating means connected with one of said time delay drive means foractuating said system; and

circuit means connecting said loads to the respective main switches toform units and the auxiliary switch of each unit with the time delaydrive means of the succeeding unit whereby when said system is actuated,the time delay drive means of the first unit will be energized to, aftera time delay, close the main and auxiliary switches of the first unit toenergize the load of the first unit and the time delay means of thesucceeding unit.

2. Sequential loading control system as set forth in claim 1 thatincludes:

pivot means mounting said respective arms to said housings whereby theangular settings of said arms may be adjusted to set the contact forcebetween set movable and stationary contacts at different selectedsettings.

1. Sequential loading control system comprising: a plurality of loads; aplurality of relay housings; respective main switches mounted in therespective housings and including respective first and second contacts,thermostatic blade means mounted on one end to said respective housingsand carrying said respective second contacts on the free ends thereoffor travel through a path into engagement with said respective firstcontacts upon flexure of said respective blade means; respectiveauxiliary switches mounted in the respective housings and includingrespective stationary contacts and elongated resilient and electricallyconductive arms mounted on one end from the respective housings andhaving the free ends thereof formed to define respective housings andhaving the free ends thereof formed to define respective movablecontacts disposed for engagement with the respective stationary contactsupon flexure of said respective arms, said arms being mechanicallycoupled with the respective thermostatic blades to form respectiveunits; respective time delay drive means including heat motors disposedadjacent each thermostatic blade; actuating means connected with one ofsaid time delay drive means for actuating said system; and circuit meansconnecting said loads to the respective main switches to form units andthe auxiliary switch of each unit with the time delay drive means of thesucceeding unit whereby when said system is actuated, the time delaydrive means of the first unit will be energized to, after a time delay,close the main and auxiliary switches of the first unit to energize theload of the first unit and the time delay means of the succeeding unit.2. Sequential loading control system as set forth in claim 1 thatincludes: pivot means mounting said respective arms to said housingswhereby the angular settings of said arms may be adjusted to set thecontact force between set movable and stationary contacts at differentselected settings.